Voltage of an alternator is proportional to

Question

Examoogle · Accepted Answer

Option B: Flux per pole

Explanation & Concepts:
The RMS voltage generated in an alternator's stator winding is directly proportional to the number of turns in the coil, the flux per pole, and the frequency of rotation. This relationship is governed by the fundamental EMF equation derived from Faraday's Law of Induction.

Working Principle: The alternator operates on the principle of electromagnetic induction where a rotating magnetic field cuts across stationary stator conductors. As the magnetic flux $\Phi$ changes with respect to time due to rotation at frequency $f$, an EMF is induced. Since the induced EMF is $E = 4.44 f N \Phi K_w$, the voltage is linearly dependent on frequency, number of turns per phase, and flux per pole.

Key Formulas: $E = 4.44 f N \Phi K_w$ — EMF equation of an alternator where $E$ is phase voltage, $f$ is frequency, $N$ is number of turns, $\Phi$ is flux per pole, and $K_w$ is the winding factor.

Key Points: Induced EMF depends linearly on the rate of flux linkage change ($d\Phi/dt$).; Increasing flux per pole ($\Phi$) increases the flux density, directly raising the induced voltage.; Higher frequency ($f$) implies faster change of flux linkage, resulting in higher induced voltage.; Total induced voltage is the sum of voltages induced in series-connected turns ($N$).

Advantages: High efficiency in power generation.; Flexibility in voltage control via field excitation.

Disadvantages: Requires complex excitation systems for voltage regulation.; Subject to synchronization requirements.

Applications: Thermal power plants; Hydroelectric power stations

Additional Info: The factor 4.44 is derived from $2\pi / \sqrt{2} \approx 4.44$ for a sinusoidal waveform.. Option B is correct, but since A and C are also correct, D is the encompassing answer.

Answer: D is correct — The induced EMF in an alternator is defined by the product of frequency, flux per pole, and winding turns, making it proportional to all three factors.

Exam Tip: Always remember the relation $E \propto f\Phi$; in variable frequency drives or speed control, this constant $V/f$ ratio is critical to prevent saturation of the magnetic core.

Examoogle · Answer

Option A: Number of turns in coil

Examoogle · Answer

Option C: Frequency

Examoogle · Answer

Option D: All of above

Correct Answer

Discussion (0)

Correct Answer

Related Questions

Discussion (0)